Without limiting the scope of the invention, its background is described in connection with microcomputers, as an example.
Glitches can occur on clock inputs due to ringing and overshoots on the input buffer, or noise superimposed on the clock input. These glitches can cause extra increments of the clock logic. A Schmitt-trigger can be used to clean up edges when the clock is switching. However, Schmitt-triggers have hysteresis, which causes the high and low threshold level to be different if the input switches high than if the input switches low. This decreases the margins for low and high input voltage specifications. Large glitches may cause input circuitry to fail.